Oil pump for a reciprocating hermetic compressor

ABSTRACT

An oil pump for a reciprocating hermetic compressor comprising a pump body ( 11 ), having a free end ( 12 ) immersed in the oil, and an opposite end ( 13 ) coupled to the compressor, so as to be driven by the latter in a reciprocating axial movement, said pump body ( 11 ) defining at the free end ( 12 ) thereof a valve seat ( 15 ), and further lodging a sealing means ( 20 ), which is displaced between a closing position, seated on said valve seat ( 15 ), and an opening position, spaced from said valve seat ( 15 ), said positions resulting from the displacements of approximation and spacing of the pump body ( 11 ) in relation to the sealing means ( 20 ) therewithin.

FIELD OF THE INVENTION

[0001] The present invention refers to an oil pump construction for areciprocating hermetic compressor of the type used in smallrefrigeration appliances, such as refrigerators, freezers, waterfountains, etc., particularly applied to a conventional reciprocatingcompressor or to that type of compressor driven by a linear motor.

BACKGROUND OF THE INVENTION

[0002] In hermetic compressors for commercial and residentialrefrigeration, an important factor for the correct operation of theappliance is the adequate lubrication of the components movingrelatively to each other. The difficulty in obtaining such lubricationis associated to the fact that the oil must flow upwardly, in order tolubricate said parts with relative movement. Among these known solutionsfor obtaining such lubrication, there is one using the principles ofcentrifugal force and mechanical dragging.

[0003] In one of these solutions, which is used both in the linearcompressors and the reciprocating compressors, in order to supply oil tothe piston/cylinder assembly, it is necessary to make the gas flow, atthe suction side of the compressor and which generates a small pressuredifferential in relation to the oil sump, draw said oil through acapillary tube, mixing it with the gas drawn by the compressor, saidmixture being admitted to the inside of the cylinder by the suctionvalve, so that the oil lubricates the contacting parts between thepiston and the cylinder. As a function of the low gas flow drawn by thecompressor in certain situations, this construction is not alwaysefficient.

[0004] In another known construction (WO97/01033), the compression andsuction forces of the piston are used to displace the lubricating oilfrom the sump, through a capillary tube, to an upper reservoir formedaround the cylinder, said reservoir being connected to the inside of thecylinder by a plurality of orifices formed in the wall thereof and whichserve for admitting oil into the piston-cylinder gap, when the piston isperforming the suction movement, and for discharging said oil when thepiston is performing the reverse movement. The oil is discharged into aplurality of channels formed in the valve plate of the compressor,further increasing the suction flow and allowing said oil to re-enterthe cylinder.

[0005] Other known solution (WO 97/01032) uses a resonant mass thatreciprocates inside a cavity formed in the external side of thecylinder, said resonant mass drawing oil from the sump while moving toone direction, said oil passing through a tube and through a one-wayvalve, which allows only the oil to enter said cavity, said cavity beingconnected to the inside of the cylinder by a plurality of orificesformed in the wall thereof. The oil in said cavity is expelled when theresonant mass moves to the other direction and passes through a one-wayvalve, which allows only the oil to leave said cavity. Although beingfunctional, this solution is difficult to produce and its constructionhas many components.

SUMMARY OF THE INVENTION

[0006] Thus, it is an object of the present invention to provide an oilpump for a reciprocating hermetic compressor, of low cost and easyconstruction, which allows to perform an adequate lubrication of thecompressor parts with relative movement, without the difficultiespresented by the known prior art solutions and without the lowefficiency of said solutions.

[0007] This and other objects are achieved by an oil pump for areciprocating hermetic compressor presenting a shell, which defines inthe interior thereof an oil sump, and which lodges a cylinder, insidewhich reciprocates a piston driven by an actuator, said oil pumpcomprising a tubular pump body, having a free end immersed in the oil,and an opposite end connected to a lubricant oil directing tube, whichconducts said oil to the compressor parts with relative movement, saidpump body defining, at the free end thereof, a valve seat, and furtherlodging a sealing means, which is displaced between a closing position,seated on said valve seat, and an opening position, spaced from saidvalve seat, the opening and closing positions being obtained when thereciprocating movement causes, respectively, a displacement ofapproximation and spacing of the pump body in relation to the sealingmeans therewithin.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention will be described below, with reference to theattached drawings, in which:

[0009]FIG. 1 is a schematic longitudinal diametrical sectional view ofpart of a reciprocating hermetic compressor with a linear motor,presenting a piston with a vertical axis and having an oil pumpconstructed according to an embodiment of the present invention;

[0010]FIG. 2 is a schematic longitudinal diametrical sectional view ofpart of a reciprocating hermetic compressor with a linear motor,presenting a piston with a horizontal axis, constructed according to theembodiment of the present invention illustrated in FIG. 1;

[0011]FIGS. 3a, 3 b and 3 c represent, schematically, the operation ofthe oil pump of the present invention illustrated in FIG. 1;

[0012]FIGS. 4a and 4 b represent, schematically, two oil pumps of thepresent invention, which are offset from each other by 90° and affixedto an eccentric of a crankshaft of a reciprocating hermetic compressor;

[0013]FIGS. 5a and 5 c represent, schematically, the operation of otherconstructive form for the oil pump of the present invention, in whichsaid oil pump is in the horizontal position.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0014] The present invention will be described in relation to areciprocating hermetic compressor (for example of the type applied to arefrigeration system) having a shell 1 lodging a cylinder 2, insidewhich reciprocates a piston 3, inside the shell 1 being defined an oilsump 4, wherefrom the lubricating oil of the movable parts of thecompressor parts is pumped by an oil pump 10.

[0015] In an illustrated constructive option (FIGS. 1 and 2), thereciprocating hermetic compressor is driven by a linear motor and thepiston 3 by an actuator 5.

[0016] In other constructive option, to be described ahead (illustratedin FIGS. 4a-4 c), the reciprocating hermetic compressor is of the typedriven by a crankshaft 6 that moves the piston 3.

[0017] In the reciprocating hermetic compressor with a linear motor, thereciprocating movement of the piston 3 is performed by the actuator 5,which supports a magnetic component driven by the linear motor. Thepiston 3 is connected to a resonant spring 7 by a connecting rod andforms, with said resonant spring and with the magnetic component, theresonant assembly of the compressor. The non-resonant assembly of thecompressor comprises the cylinder 2, a suction and a discharge systemand its linear motor.

[0018] According to the present invention, the oil pump 10 comprises atubular pump body 11, having a free end 12 immersed in the oil, and anopposite end 13 connected to a lubricant oil directing tube 14, whichconducts oil from the oil sump 4, said oil being pumped by the pump body11 to the compressor parts with relative movement, particularly betweenthe piston 3 and the internal wall of the cylinder 2.

[0019] The pump body 11 is coupled to the compressor, in order to bedriven in a reciprocating axial movement caused by operation of saidcompressor, when the latter vibrates as a function of the mutualreactions of resonance forces, which are related to the oscillatingmasses therein, with an oscillation amplitude, which is a function ofthe ratio of the mass of the piston (and aggregated parts thereof) tothe mass of the compressor.

[0020] The pump body 11 defines in the free end 12 thereof a valve seat15 and also lodges a sealing means 30, which is displaced between aclosing position, seated on said valve seat 15, and an opening position,spaced from said valve seat 15, the opening and closing positions beingobtained when the reciprocating movement causes, respectively, adisplacement of approximation and spacing of the pump body 11 inrelation to the sealing means 20 therewithin.

[0021] In the illustrated embodiment, the valve seat 15 is defined in atapered portion of the pump body 11, adjacent to the free end 12thereof.

[0022] According to the present invention, the oil pump 10 has its pumpbody 11 coupled to the compressor by means of a lubricant oil directingtube 14.

[0023] The actuation of the present oil pump by the compressor occurs,for example, as a function of the oscillating movements of saidcompressor, such as that resulting from the reaction forces of theresonant assembly. Such oscillating movement is possible, since thecompressor is supported by suspension springs.

[0024] In the constructions of a hermetic compressor with a linearmotor, the lubricant oil directing tube 14 is affixed to the compressor,for example, by interference of one fixing end 14 a thereof to a channel2 a provided in the body of the cylinder 2 (FIGS. 1 and 2) and whichusually presents a substantially vertical development (FIG. 1).Nevertheless, said channel 2 a may have part of its extensionsubstantially horizontal, as it occurs in the constructions having thelinear motor with a horizontal axis (FIG. 2).

[0025] In the solution of the present invention, the pumping mechanismdepends on the inertia effect of the oil contained in the lubricant oildirecting tube 14. This oil column generates a flow when the movement isdownward and the sealing means 20 avoids, in the upward movement, theoil from flowing out from said lubricant oil directing tube 14.

[0026] According to a constructive option of the present invention,illustrated for compressors with a linear motor (FIGS. 1 and 2), theoperation and movement of the oil pump is determined, for example, bythe reciprocating movement of the compressor inside the shell 1,oscillating according to the oscillating movement of the assembly ofsprings 8 that support the compressor (FIGS. 1 and 2), in the sameoscillating direction of these springs 8. It should be emphasized thatthis vibration of the compressor results from the mounting thereof tothe shell by suspension springs. If the compressor were not mountedinside the shell by springs, such vibrations would not exist.

[0027] In the constructions in which the reciprocating compressor has acrankshaft 6 (FIGS. 4a to 4 c), the movement and operation of the oilpump of the present invention is determined, for example, by movement ofsaid crankshaft 6 (FIGS. 4 to 4 b). In this case, the lubricant oildirecting tube 14 is eccentrically affixed to the eccentric of thecrankshaft 6, orthogonal to the axial axis thereof, such that therotation of the crankshaft 6 results, during operation of thecompressor, in an axial displacement of the present oil pump, spacingfrom and approximating to the oil sump 4.

[0028] In the illustrated constructions, the lubricant oil directingtube 14 comprises a tubular extension, which is affixed, by a receivingend 14 b, to an adjacent end of the pump body 11, opposite to that endimmersed in the lubricating oil with the fixing end 14 a thereof coupledto the compressor.

[0029] According to a constructive form of the present invention,illustrated in FIGS. 3a-3 c, the sealing means 20 is a floating element,for example presenting a substantially spherical contour, which isprovided inside the pump body 11 and floats between the valve seat 15and a position inside the pump body 11 spaced from said valve seat 15,as a function of the movement of the compressor element that actuatesthe displacements of the sealing means 20.

[0030] In the illustrated constructive options, the spacing displacementof the sealing means 20 in relation to the valve seat 15 is limited by astop means, which is defined inside the pump body 11 spaced from saidvalve seat 15.

[0031] In an illustrated construction (FIGS. 3a to 3 c), the stop meansis defined, for example, by a radial projection 16, internal to the pumpbody 11 and positioned at a determined distance from the valve seat 15thereof, and occupying, at minimum, a certain extension transversal tothe longitudinal axis of said pump body 11, sufficient to prevent thefree and unlimited displacement of the sealing means 20 inside said pumpbody 11.

[0032] The determined distance between the valve seat 15 and the stopmeans inside the pump body 11 is defined so as to optimize the oilpumping in the compressor.

[0033] In another embodiment of the present invention illustrated inFIGS. 5a-5 c, the stop means is in the form of a spring element 36having an end portion mounted to the opposite end 13 of the pump body11, and another end portion coupled to the sealing means 20, said springelement 36 defining, in a first operative position, the opening positionof the sealing means 20, and in a second operative position, the closingposition of said sealing means 20.

[0034] According to the illustrated embodiment in FIGS. 5a-5 c, thesealing means 20, when in its opening position, presses the springelement 36 to a maximum value that determines the opening limit of saidsealing means 20.

[0035] In a constructive option, the spring element 36 further presentsan inoperative resting position (FIG. 5b), intermediate to the first andsecond operative positions and in which the sealing means 20, whenaffixed to the other end portion of the spring element 36, remainsspaced from the valve seat 15 and prevented from seating on the springelement 36. This inoperative position is obtained when the compressor isnot operating.

[0036] Although an embodiment with stop means in the form of a springelement 36 mounted in the pump body 11 has been illustrated, it shouldbe understood that said mounting may be effected, for example, in anyinternal portion of the pump body 11, such as the radial projection 16.It should be further understood that the sealing means 20 may beprovided inside the pump body 11, when the stop means is defined by thefloating spring element 36, the opening position of the sealing means 20being obtained by the latter exerting pressure over the spring element36, resulting from the operation of the compressor.

[0037] Although FIGS. 5a-5 c illustrate a construction in which the oilpump of the present invention is horizontal, it should be understoodthat this embodiment may also be applied to the constructions in whichthe oil pump 10 is vertical.

1. An oil pump in [for] a reciprocating hermetic compressor presenting ashell (1), which defines in the interior thereof an oil sump (4), andwhich lodges a cylinder (2), inside which reciprocates a piston (3),characterized in that it comprises a tubular pump body (11), having afree end (12) immersed in the oil, and an opposite end (13) connected toa lubricant oil directing tube (14), which conducts said oil to thecompressor parts with relative movement, said pump body (11) beingcoupled to the compressor, so as to be actuated in a reciprocating axialmovement, said pump body (11) defining at the free end (12) thereof avalve seat (15), and further lodging a sealing means (20), which isdisplaced between a closing position, seated on said valve seat (15),and an opening position, spaced from said valve seat, the opening andclosing positions being obtained when the reciprocating movement causes,respectively, a displacement of approximation and spacing of the pumpbody (11) in relation to the sealing means (20) therewithin.
 2. Oilpump, according to claim 1, characterized in that the fixation of thepump body (11) to the compressor is effected by the lubricant oildirecting tube (14).
 3. Oil pump, according to claim 2, characterized inthat the lubricant oil directing tube (14) is affixed to the cylinder(2).
 4. Oil pump, according to claim 3, and in which the compressor isof the reciprocating type having a crankshaft (6) for driving the piston(3), characterized in that the lubricant oil directing tube (14) iseccentrically affixed to the crankshaft (6), orthogonal to the axialaxis thereof.
 5. Oil pump, according to claim 3, and in which thecompressor is driven by a linear motor, characterized in that themovements of the pump body (11) are obtained by vibration of thecompressor.
 6. Oil pump, according to claim 1, characterized in that itcomprises a stop means (16, 36), which is provided inside the pump body(11) spaced from the valve seat (15) thereof, and which limits thedisplacement of approximation and spacing of the pump body (11) inrelation to the sealing means (20) therewithin.
 7. Oil pump, accordingto claim 6, characterized in that the stop means is defined by a radialprojection (16) internal to the pump body (11) and positioned at adetermined distance from the valve seat (15) thereof.
 8. Oil pump,according to claim 1, characterized in that the stop means is defined bya spring element (36) having an end portion mounted to the pump body(11), and another end portion coupled to the sealing means (20), saidspring element (36) defining, in a first operative position, the openingposition of the sealing means (20), and in a second operative position,the closing position of the sealing means (20).
 9. Oil pump, accordingto claim 8, characterized in that in the first operative position thesealing means (20) exerts pressure over the spring element (36).
 10. Oilpump, according to claim 9, characterized in that the spring element(36) presents an inoperative position intermediate to the first andsecond operative positions.
 11. Oil pump, according to claim 9,characterized in that the spring element (36) has the end portionthereof mounted to the opposite end of the pump body (11).
 12. Oil pump,according to claim 9, characterized in that the spring element (36) hasthe other end portion thereof mounted to the sealing means (20).
 13. Oilpump, according to claim 1, characterized in that the sealing means (20)is a floating element provided inside the pump body (11).
 14. Oil pump,according to claim 13, characterized in that the sealing means (20) is asubstantially spherical body.